1. Field of the Invention
The present invention relates to power management in a computer system having multiple devices, such as in a rack-based server system or data center.
2. Description of the Related Art
Multiple servers and other computer hardware are often consolidated into a centralized data center. Servers in a data center may be mounted in a rack to conserve space and place the servers and infrastructure within easy reach of an administrator. The IBM eServer BLADECENTER is one example of a compact server arrangement (IBM and BLADECENTER are registered trademarks of International Business Machines Corporation, Armonk, N.Y.).
When multiple servers and other computing hardware are consolidated, power to the servers must be carefully monitored and controlled. Power consumption affects many aspects of operating a data center, such as the costs of operating the servers, the heat generated by the servers, and the performance and efficiency of the system. The individual servers and the system as a whole are limited by design parameters such as maximum power consumption, maximum operating temperature, processing efficiency, and so forth. Thus, it is important to control power to the system in consideration of these parameters.
Existing processing systems may be powered by a common power supply or power distribution unit (PDU). Some of the systems include a circuit, such as a Baseboard Management Controller (BMC), that can monitor real-time power consumption by a server. Using this feedback, the BMC can “throttle” or “speed-step” the processors and/or memory on the server to maintain the power consumption below a set point or “power ceiling” set by an administrator and monitored by the chassis management module. U.S. Pat. No. 7,155,623 to IBM discloses a “Method and System for Power Management Including Local Bounding of Device Group Power Consumption.” U.S. Patent Application Publication No. US 2006/0156042 to IBM discloses a “Method, System, and Calibration Technique for Power Measurement and Management Over Multiple Time Frames.”
However, speed-stepping the processors can only bring about a limited reduction in power consumption. When there is a critical need for greater power reductions than can be achieved by speed-stepping the processors, then the typical solution is to power off one or more of the blade servers within the power distribution unit. Unfortunately, shutting off the power to a blade server causes a loss of user data.
Therefore, there is a need for improved power management systems and methods that can achieve large reductions in power consumption without loss of user data. It would be desirable for the improved power management systems and methods provided greater flexibility in selecting where and how power consumption will be reduced, so that system performance is maintained or optimized under the prevailing power constraints.